There are important days in our memories. The day we graduated, the day we were married, the day we started or ended employment. September 11, 2001, is a day that is burned into the collective memory of America.

Millions of people watched their TV screens with horror that day as the second 747 blasted into the South Tower 18 minutes after the North Tower had been struck. We understood without doubt that this was not a crazy accident, but an orchestrated attack.

An unintended consequence of the 9/11 attacks developed as we contemplated why the terrorists attacked where they did. The Twin Towers of the World Trade Center were targeted to punch a fist into our economy. The attack on the Pentagon was a slug in the face of the US military. The last plane, which was crashed by its passengers into a Pennsylvania field to protect the last target, was thought to be heading toward the Capitol or White House, a strike at our Constitutional form of government. Their choices awakened America to its own uniqueness. America, the land of opportunity, the land of the free, and home of the brave. If we had failed to understand what America means to the rest of the world, evil terrorists, in trying to destroy us, defined us to ourselves.

I have a photograph of my father standing on the pedestal of the Statue of Liberty, taken when he played for the New York Giants in 1952. There are skyscrapers in the background, but nothing too distinct. I have another picture of myself taken from the same place in 1996, with the Twin Towers identifying the Manhattan skyline. On a recent trip, I photographed One World Trade Center’s mirror windows reflecting the new life that has sprung up from the ashes.

It’s been 18 years, yet we still remember how we yearned to put our collective arms around our fellow citizens and weep together. How many dead? How many hurt? When should we give up hope for survivors? When and where would our self-proclaimed enemies strike again? We wanted to protect each other.

Now, rising majestically beside the place where the Twin Towers once stood, is One World Trade Center. It’s the tallest building in New York City and the Western Hemisphere. Its faceted walls soar into the heavens and reflect the commerce, citizens, enterprises and landscapes that surround it.

The Pentagon, the US center for military control, lies in Virginia, not far from Arlington National Cemetery. From the highway, passers cannot tell that it’s shaped like a pentagon. The physical scars from the attack have been obliterated. But inside, the war to protect American ideals continues.

The memorials for the Twin Towers are the tallest manmade waterfalls in North America. The memorial design by architect Michael Arad and landscape architect Peter Walker was chosen from 5,200 entries in a global design competition.

Now, there are two huge, nearly identical water features built in the footprints of each of the towers. They are each nearly an acre, square pits with water falling into the pit from the rim and into a second, deeper pit in the middle of each. They are covered in black stone. The outer rims are lined with bronze plates that bear the names of all 2,977 people killed in the attacks and the additional six people killed in the first terror attack on the World Trade Center in February 1993.

The majority of those who died that day were ordinary civilians. But hundreds of first responders rushed to the site to begin the rescues. Firefighters focused their attention on rescuing victims. Many returned in and out of the towers, evacuating victims below the level of the strike. They were well-trained, brave and heroic men who knew what the price could be each time they returned to the burning tower. They did it anyway.

412 firefighters, police and medical technicians gave their lives that day. It seems to me that those people truly embody the ultimate heroism. Jesus said, “Greater love hath no man than this, that a man lay down his life for his friends.”

I suppose those who sacrificed themselves on Sept. 11, 2001, considered all their countrymen friends.